calculating log_buffer size
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  1. #1
    Join Date
    Apr 2001
    Location
    London
    Posts
    725
    HI Folks,

    I am currently trying to attain the size of my redo log buffer. I have read that the log buffer size in init.ora is to be multiplied by the OS block size to establish amount in bytes allocated. My log buffer size parameter is currently 163840.

    I beleive my OS block size is either 2048 or 1024.
    To prove this I did a :

    select * from v$sgastat

    The log buffer size was 163840 bytes.

    I would have expected this to be at least :-
    167772160 (163840 * 1024)

    Can anyone plese explain.

    Cheers

    Suresh

  2. #2
    Join Date
    Apr 2001
    Location
    London
    Posts
    725

    Also..

    I executed the following sql to find ratio.

    SELECT REQ.VALUE|| ':' ||ENTRIES.VALUE "SPACE REQUEST RATIO"
    FROM V$SYSSTAT REQ,V$SYSSTAT ENTRIES
    WHERE REQ.NAME='redo log space requests'
    AND ENTRIES.NAME='redo entries'

    Results

    53:1684533

    = 1 : 31783

    I have also read that the ratio should be no more than
    1 : 5000

    does this mean that I nead to increas the log_buffer size ?

    Cheers

    Suresh

  3. #3
    Join Date
    Mar 2001
    Posts
    65

    as i understand log_buffer is specified in bytes though internally it's divided into os_block_size buffers for writing to redo log files.

    ajay

  4. #4
    Join Date
    Apr 2001
    Location
    London
    Posts
    725
    Thanks for your reply,

    However, do you know why the log_buffer size is a smaller number when omitting a 'show sga' in sqlplus.
    And do you have any suggestions regarding my second question - ratio of requests to entries.

    Cheers

    Suresh

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